Iron is used for treatment of anemia and as a prenatal or daily mineral supplement. Owing to wide availability and presumed harmlessness as a common over-the-counter nutritional supplement, it remains a common (and potentially fatal) childhood ingestion. There are many iron preparations that contain various amounts of iron salts. Most children's preparations contain 12–18 mg of elemental iron per dose, and most adult preparations contain 60–90 mg of elemental iron per dose. The following description of the toxicity of iron relates to the ingestion of iron salts (eg, sulfate, gluconate, fumarate). Products such as carbonyl iron and iron polysaccharide complex have not been reported to produce the same syndrome of toxicity.
Mechanism of toxicity. Toxicity results from direct corrosive effects and cellular toxicity.
Iron has a direct corrosive effect on mucosal tissue and may cause hemorrhagic necrosis and perforation. Fluid loss from the GI tract results in severe hypovolemia.
Absorbed iron, in excess of protein-binding capacity, causes cellular dysfunction and death, resulting in lactic acidosis and organ failure. The exact mechanism for cellular toxicity is not known, but iron ligands cause oxidative and free radical injury.
Toxic dose. The acute lethal dose in animal studies is 150–200 mg/kg of elemental iron. The lowest reported lethal dose was in a 21-month-old child who was said to have ingested between 325 and 650 mg of elemental iron in the form of ferrous sulfate. Symptoms are unlikely if less than 20 mg/kg of elemental iron has been ingested. Doses of 20–30 mg/kg may produce self-limited vomiting, abdominal pain, and diarrhea. Ingestion of more than 40 mg/kg is considered potentially serious, and more than 60 mg/kg is potentially lethal. Even though they contain iron salts, there are no reported cases of serious or fatal poisoning from the ingestion of children's chewable vitamins with iron. The reason for this is unclear.
Clinical presentation. Iron poisoning is usually described in four stages, although the clinical manifestations may overlap.
Shortly after ingestion, the corrosive effects of iron cause vomiting and diarrhea, often bloody. Massive fluid or blood loss into the GI tract may result in shock, renal failure, and death.
Victims who survive this phase may experience a latent period of apparent improvement over 12 hours.
This may be followed by an abrupt relapse with coma, shock, seizures, metabolic acidosis, coagulopathy, hepatic failure, and death. Yersinia enterocolitica sepsis may occur.
If the victim survives, scarring from the initial corrosive injury may result in pyloric stricture or other intestinal obstructions.
Diagnosis is based on a history of exposure and the presence of vomiting, diarrhea, hypotension, and other clinical signs. Elevation of the white blood cell count (>15,000/mm3) or blood glucose (>150 mg/dL) or visible radiopaque pills on abdominal radiograph also suggest significant ingestion. Serious toxicity is unlikely if the white cell count, glucose, and radiographic findings are normal and there is no spontaneous vomiting or diarrhea.
Specific levels. If the total serum iron level is higher than 450–500 mcg/dL, toxicity ...